1. Field of the Invention
The present invention relates to an air conditioner having a high heating capacity, and more particularly to an air conditioner, with a compressor driven by an engine, having a high heating capacity,
2. Description of the Related Art
A conventional air conditioner, whose compressor is driven by an engine as shown in FIGS. 7 and 8, is disclosed in the Service Manual of the Heat-pump type air conditioner (issued by Aisin Seiki Co., Ltd. in July, 1989). Referring to FIG. 7, when a user turns on a switch (not shown), the air conditioner 500 is driven. An engine 510 is started and a compressor 530 is driven. A vapor refrigerant is discharged from the compressor 530, and flows into an indoor heat exchanger 531 via an oil separator 532 and a reversing valve 533. The indoor heat exchanger 531 is located in an indoor unit 534. An indoor air flow is generated in the indoor unit 534 by a fan 535. Heat radiation from the refrigerant to the indoor air is established, and the indoor air becomes hot. Further, the vapor refrigerant condenses into liquid refrigerant.
After that, the liquid refrigerant flows into an expansion valve 536 via a receiver 537. The opening ratio of the expansion valve 536 is regulated by a temperature detecting tube 538, so that all of the liquid refrigerant flowing into the first expansion valve 536 does not flow therethrough. Thus, one part of the liquid refrigerant is temporarily kept in the receiver 537.
When the liquid refrigerant flows through the first expansion valve 536, the liquid refrigerant expands and changes into liquid and vapor refrigerant. Next, the liquid and vapor refrigerant flows into an outdoor heat exchanger 539. The outdoor heat exchanger 539 is located in an outdoor unit 540. An outdoor air flow is generated in the outdoor unit 340 by a fan 541. Here, heat transfer from the outdoor air to the refrigerant is established, and the liquid and vapor refrigerant evaporate completely. This complete evaporation of the liquid and vapor refrigerant is ensured by the regulation of the opening ratio of the expansion valve 536. After that, the vapor refrigerant flows into the compressor 530 via the reversing valve 533 and an accumulator 542.
Referring to FIG. 8, a coolant discharged from a water pump 550 flows through the engine 510 and into an exhaust heat exchanger 551, thus increasing a temperature of the coolant. Next, the hot coolant flows into a hot coolant heat exchanger 552. Here, heat radiation from the hot coolant to the indoor air is established, and the indoor air becomes hot, too. Therefore, the room (not shown) is heated by the refrigerant and the hot coolant.
When the outdoor temperature is too low, an evaporating temperature and an evaporating pressure of the liquid and vapor refrigerant in the outdoor heat exchanger 539 become low. Further, density of the vapor refrigerant which is sucked into the compressor 530 becomes low and mass flow of the refrigerant in a heat-pump circuit becomes little. As a result, the quantity of the heat transfer from the outdoor air to the refrigerant becomes low, and a quantity of the heat radiation from the refrigerant to the indoor air decreases. On the other hand, the work load of the compressor 530 decreases. That is, the work load decreases since a suction pressure of the compressor 530 is relatively low. As a result, the load of the engine 510 decreases according to the decreasing of the work load of the compressor 530, and a temperature of the coolant decreases, so that a quantity of the heat radiation from the hot coolant to the indoor air at the hot coolant heat exchanger 552 decreases. Thus, the heating capacity according to the refrigerant and the coolant of the air conditioner 500 decreases.